EP0435433B1

EP0435433B1 - Water content monitor apparatus and method

Info

Publication number: EP0435433B1
Application number: EP90311467A
Authority: EP
Inventors: John David Marrelli
Original assignee: Texaco Development Corp
Current assignee: Texaco Development Corp
Priority date: 1989-12-26
Filing date: 1990-10-18
Publication date: 1997-04-23
Anticipated expiration: 2010-10-18
Also published as: DE69030562T2; CA2020351A1; EP0435433A3; NO304331B1; US5140271A; NO905065D0; EP0435433A2; NO905065L; DE69030562D1; DK0435433T3

Description

The present invention relates to water content monitors for monitoring the percentage water content in a flowing fluid stream, in particular a petroleum stream. Such monitors are referred to in the following description as watercut monitors, and particularly microwave watercut monitors.
US-A-4499418 describes a water content monitor for monitoring the percentage water content in a flowing fluid stream, comprising:

a test cell arranged for flow of the fluid stream therethrough;
a first antenna for irradiating the flow through the test cell with microwave energy;
a second antenna for receiving microwave energy transmitted through the flow;
means to provide a signal representative of the phase difference between the microwave energy from the source and the received microwave energy; and
means to provide a signal representative of the percentage water content of the fluid stream in accordance with said phase difference signal.

The present invention is characterized in that:

said monitor is adapted to monitor the water content in a petroleum stream flowing through said test cell;
a detector is connected to said second antenna to detect the intensity of the received energy and to provide a signal representative thereof, said means providing its signal in accordance with said intensity signal and said phase difference signal;
said first and second antennae are disposed within said test cell;
a first waveguide is disposed to conduct microwave energy from a source to the first antenna, and a second waveguide is disposed to conduct received microwave energy from the second antenna to said detector;
screen means is provided within the test cell to substantially prevent particulate matter of greater than a predetermined size from entering within said screen means; and
said first and second antennae are disposed within said screen means to reduce the amount of particulate material in the portion of the petroleum stream which flows between said antennae, the screened-out particulate matter being carried away by the petroleum stream flow outside said screen means.

US-A-3946308 describes apparatus for measuring the humidity of a gas such as air. There is no test cell or pipeline. There are spaced input and output microwave antennae surrounded by a cylindrical guard dimensioned to minimize the escape of microwave energy. This forms a resonator placed in an atmosphere of humid air. In one embodiment the top and bottom are covered by lids made of a copper wire net for keeping out dust and foreign matters.
US-A-4822486 describes a rotary strainer attached to the end of a conduit and immersed in a body of water. Impairment of flow by adhered debris is prevented by rotating the screen past a nozzle structure from which water is fed under pressure through a separate supply line which may be taped into the pumps remote outlet.
The present invention is exemplified in the detailed description which follows, taken together with the accompanying drawings wherein one embodiment is illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustrative purposes only and are not to be construed as defining the limits of the invention.
Figure 1 is a simplified block diagram of a microwave watercut monitor constructed in accordance with the present invention.
Figure 2 is a representation of the test cell shown in Figure 1.
Figure 3 is a detailed representation of the test cell shown in Figure 1.
Figure 4 is a cross sectional view along the lines 4- 4 of the test cage shown in Figure 3
The watercut monitor shown in Figure 1 includes a microwave transmitter 3 providing electromagnetic energy, hereinafter referred to as microwave energy, at a microwave frequency. Transmitter 3 is low powered and may use a microwave gun source. Transmitter 3 provides microwave energy to directional coupler 7. Directional coupler 7 provides microwave energy to a conventional type voltage controlled phase shifter 9 and to a circulator 8. All conductance or carrying of microwave energy is accomplished by using conventional type waveguides.
Circulator 8 provides microwave energy via a waveguide 10, to a petroleum stream passing through a test cell 17. Test cell 17 will be described in greater detail hereinafter. The microwave energy that passes through the petroleum stream is provided by way of a waveguide 19 to a switch means 24 which when in one state provides received microwave energy as test microwave energy to a directional coupler 28. Directional coupler 28 provides the test microwave energy to a detector 32 and to a mixer 34. Detector 32 provides a signal E2 corresponding to the intensity of the test microwave energy.
The petroleum stream may also reflect some of the microwave energy back which passes back to circulator 8 by way of waveguide 10. Circulator 8 blocks the reflected microwave energy from feeding back to transmitter 3 and provides the reflected microwave energy which becomes more important as the distance across test cell 17 increases. This is especially true where test cell 17 is used with a large pipeline carrying the petroleum stream.
A positive direct current voltage +V is provided to switch means 24. With switch means 24 in another state, switch means 24 provides the reflected microwave energy from circulator 8 as the test microwave energy.
The microwave energy from voltage control phase shifter 9, hereinafter called the reference microwave energy, and the test microwave energy from directional coupler 28, are provided to mixer 34 which mixes them to provide two electrical signals E3, E4, representative of the phases of the reference microwave energy and the test microwave energy, respectively.
A differential amplifier 36 provides an output signal EO in accordance with the difference between the signals E3, E4 and hence the phase difference between the test microwave energy and the reference microwave energy. Signal EO, and hence the signal C, decreases in amplitude until there is substantially 90° phase difference between the reference microwave energy and the test microwave energy. Voltage control phase shifter 9 indicates the amount of phase shift required to eliminate the phase difference and provides an "enable" signal to computer means 50.
Signals E2 and C are provided to computer means 50 which contains within its memory means data related to phase and amplitude for various percentages of watercuts that could be encountered in the production stream. The "enable" signal, provided by phase shifter 9 to computer means 50, allows computer means 50 to utilize signals C and E1 to select the proper watercut value. Computer means 50 provides signals, corresponding to the selected watercut value, to readout means 54 which may be either digital display means or recording means or a combination of two.
With reference to Figures 2, 3, and 4, waveguide 10 enters test call 17 and a test cage 70 and is connected to an antenna 74. A seal 76 prevents any of the petroleum stream in test cell 17 from leaking out. Similarly waveguide 19 enters test cell 17 and test cage 70 is connected to an antenna 80. A seal 84 prevents the petroleum stream from leaking from test cell 17.
As shown in Figures 1 and 2, microwave energy from circulator 8 will pass through line 10 and is radiated by antenna 74 to antenna 80. Antenna 80 receives microwave energy and provides the received microwave through waveguide 19. Cage 70 is a self cleaning device that allows a fluid mixture to flow between antennas 74 and 80 while removing particles and debris that might be in the petroleum stream.
Test cage 70 has two end pieces 87 and 90 designed to support a coarse wire mesh 93 as an outside screen and a fine wire mesh 98 as an inner screen. The passage of waveguides 10 and 19 through end plates 87 and 90, respectively, is supported by a ball bearing system 102. Test cage 70 will rotate around waveguides 10 and 19 in response to the flow of the petroleum stream.
In operation, as debris in the petroleum stream comes in contact with cage 70, the larger elements of the debris makes contact with the coarse wire mesh 93 and fall to the bottom of the test cell 17 and is carried away by the flow of the petroleum stream. Smaller elements of the debris may enter cage 70 but they will come in contact with fine wire mesh 98 and be stopped from entering that portion of test cage 70 that lies between antennas 74 and 80. The debris stop by fine wire mesh 98 may be carried by fine wire mesh 98 and fall away under the influences of gravity and due to the rotation of cage 70. The fallen smaller elements will pass out of cage 70 due to the flow of the petroleum stream so that there is not a build up of debris in the vicinity of the microwave energy path between antennas 74 and 80.
The present invention as hereinbefore described is a microwave watercut monitor with apparatus for reducing the amount of debris in a petroleum stream passing between microwave antennas so as to enhance the accuracy of the watercut monitor.

Claims

A water content monitor for monitoring the percentage water content in a flowing fluid stream, comprising:
a test cell (17) arranged for flow of the fluid stream therethrough;

a first antenna (74) for irradiating the flow through the test cell with microwave energy;

a second antenna (80) for receiving microwave energy transmitted through the flow;

means (9,44) to provide a signal representative of the phase difference between the microwave energy from the source and the received microwave energy; and

means (50) to provide a signal representative of the percentage water content of the fluid stream in accordance with said phase difference signal;
characterized in that:
said monitor is adapted to monitor the water content in a petroleum stream flowing through said test cell;

a detector (32) is connected to said second antenna to detect the intensity of the received energy and to provide a signal representative thereof, said means (50) providing its signal in accordance with said intensity signal and said phase difference signal;

said first and second antennae (74,80) are disposed within said test cell (17);

a first waveguide (10) is disposed to conduct microwave energy from a source (3) to the first antenna, and a second waveguide (19) is disposed to conduct received microwave energy from the second antenna to said detector (32);

screen means (70) is provided within the test cell to substantially prevent particulate matter of greater than a predetermined size from entering within said screen means; and

said first and second antennae (74,80) are disposed within said screen means (70) to reduce the amount of particulate material in the portion of the petroleum stream which flows between said antennae, the screened-out particulate matter being carried away by the petroleum stream flow outside said screen means.
A monitor according to Claim 1 characterized in that said screen means (70) is substantially a hollow cylinder in shape having an axis extending across said flow, said screen means (70) being rotatably supported by said waveguides (10,19) for free rotation about said axis in response to said flow.
A monitor according to Claim 1 or Claim 2 characterized in that said screen means (70) comprises an outer screen (93) to substantially prevent particulate matter of greater than said predetermined size from entering within said outer screen (93), and an inner screen (98) to substantially prevent particulate matter of greater than a second predetermined size, smaller than said first size, from passing between said antennae (74,80).
A monitor according to Claim 1 characterized in that said screen means (70) comprises an outer cylindrical screen (93) of a first mesh, an inner cylindrical screen (98) of a second mesh finer than said first mesh and disposed coaxially within the outer screen (93), and end pieces (87,90) supported one each by said first and second waveguides (10,19) and supporting opposite ends of said cylindrical screens.
A monitor according to Claim 4 characterized by a bearing (102) mounted in each said end piece (87,90) to permit free rotation of said screen means (70) about the axis of said cylindrical screens (93,98) in response to said flow.